The present invention relates to the field of designing drive arrangements for driving three-phase motors whose winding legs are switchably connectable for efficient start-up.
A drive arrangement is known from "Drive Arrangement for Asynchronous and Synchronous Machines Without Phase Interruption," by Titel, Elektrotechnik und Maschinenbau, 1961, pages 163 to 170 having two winding legs per phase switchably connectable for efficient start-up. For the initial running up to speed of the motor, one winding leg of one phase is connected together with one winding leg of another phase for torque generation and connected to a supply system by means of a first switch, and, after the initial running up to speed, the winding legs are separately connected to the supply system by means of an second switch.
Further, after the running up to the speed, by the closing of the second switch, the winding legs are connected to the supply system in such a way that a double delta connection results, that is, one pair of winding legs of one delta connection is connected to the supply system, and so are one pair of winding legs of the other delta connection. Both delta connections of the winding legs are then in parallel on the supply system or network. With such a drive arrangement, a reduction of the startup current requirement to barely sixty percent of the startup current in direct startup is possible.